Terminal pins with compliant sections or portions (sometimes called press-fit pins) have been known in the art for many years. Compliant pins are designed to be inserted into a plated-through hole in a printed circuit board or other conductive plate. The pin generally includes a mating portion adapted to contact an electrically conductive element and a compliant portion extending from the mating portion and adapted to make electrical contact with conductive material defining the interior surface of the plated-through hole. Therefore, a solder-free electrical connection is made between the pin and the hole, i.e., the conductive interior surface of the hole.
Such pins provide high reliability applications without the necessity of solder. The pins should be able to withstand repeated insertions and withdrawals from the plated-through hole without damaging the interior surface of the hole. Elastic strain energy mostly should be stored in the compliant portion of the pin. The pins should be able to be used over a wide range of hole sizes to eliminate the need for different thicknesses of the plating material formed in the hole. Relatively lower insertion forces should be provided so that mass insertion is feasible. These and other characteristics of compliant pins are provided by the terminal pin of the invention as well as in compliant terminal pins of the prior art. For instance, a terminal pin with an S-shaped compliant portion is shown in U.S. Pat. No. 4,857,019 to Brubaker et al., dated Aug. 15, 1989 and assigned to the assignee of this invention.
One of the problems of most prior art compliant terminal pins is that their configurations are formed through a series of coining operations which result in work hardening of the metal forming the compliant portion of the pin. Due to this work hardening, high residual stresses, along with increased surface hardening, results in a much less ductile and inelastic compliant portion than may be desired. Coined compliant pins also are very "diameter dependent", i.e., they cannot conform to as wide a range of whole diameters and center-to-center variability between holes as might be desired. In addition, the less the flexibility of the compliant portion, the greater the possibility of piercing or cutting through the plating on the interior surface of the plated-through hole.
This invention is directed to solving the above problems and satisfying the need for a new and improved compliant terminal pin of improved elasticity of its compliant portion.